1. Field of the Invention
The present invention relates to ink-jet printers and, more specifically, to a circuit and method for controlling the print heads of an ink-jet printer, which processes print data through a single operation of memory accessing, by overcoming the distance between nozzle columns of a print head.
2. Discussion of Related Art
The print head of a typical ink-jet printer has a predetermined distance between odd-numbered and even-numbered nozzles in accordance with head type, i.e., color or monochrome, as shown in FIGS. 1A and 1B, respectively. That is, 18 nozzles are arranged in two columns on a nozzle plate 1a of a color print head, thus establishing a uniform distance L between columns of odd and even nozzles, while 56 nozzles are arranged in two columns on a nozzle plate 1b of a monochrome print head, thus establishing a uniform distance M between columns. Accordingly, during a printing operation, odd data and even data are read out of a memory with respect to the predetermined distance, L or M.
Referring to FIG. 2, a conventional circuit for controlling a print head to perform printing using the above nozzles comprises: a memory 101 for temporarily storing print data from a computer (not shown); a printer controller 102 for processing the stored print data and outputting print data suitable for a printing operation; a printer data separator 103 for separating the processed print data according to a separator select signal, to output odd nozzle data and even nozzle data; odd and even nozzle data latches 104 and 105 for latching the separated nozzle data according to latch signals applied from the printer controller 102 and thereby outputting odd data and even data, respectively; a print data control logic circuit 106 for outputting a next data request signal and outputting a print head control signal based on the separately output odd and even data, according to a fire strobe signal; a DMA/interrupt controller 107 for applying a direct memory access (DMA) or interrupt request signal to the printer controller 102 upon receiving the next data request signal; and a printer head 108 for performing a printing operation according to the print head control signal from the print data control logic circuit 106.
In the operation of the above print head controlling circuit, when a user executes a print program, the printer controller 102 temporarily stores print data in the memory 101 and processes the stored print data for output to the printer data separator 103. Here, odd data and even data are read from memory 101 according to the predetermined distance between the columns of odd and even nozzles, as shown in FIGS. 1A and 1B. In accordance with the printing direction, a DMA or interrupt request signal is applied from the DMA/interrupt controller 107 to the printer controller 102.
At this time, the printer controller 102 outputs the separator select signal to the printer data separator 103. A separator select signal for odd data means that the printer data separator 103 outputs odd nozzle data to the odd nozzle latch 104 which in turn supplies odd data to the print data control logic circuit 106. Thus, a print head control signal according to the applied odd data is generated according to the fire strobe signal and the next data request signal is supplied to the DMA/interrupt controller 107 which therefore outputs a DMA or interrupt request signal. This DMA or interrupt request signal, applied to the printer controller 102, results in a separator select signal corresponding to even data.
The even-data separator select signal is applied to the printer data separator 103 which in turn outputs even nozzle data to the even nozzle data latch 105. Similar to the case of the odd data, the print data control logic circuit 106 outputs a print head control signal according to the even data and the fire strobe output from the printer controller 102.
The printer head 108 then jets ink according to the applied print head control signal.
With the above described conventional print head controlling circuit, two DMA or interrupt request operations are needed for a single operation of data printing; i.e., first, for an odd nozzle data request, and, second, for an even nozzle data request. Such repeated processing necessitates a longer time for performing the printing operation. Furthermore, two channels of DMA or interrupt request should be provided for processing the head data, thus complicating the logic circuit.